Pipe cutting tool

ABSTRACT

A pipe cutting tool particularly adapted for cutting off PVC waste pipe or the like below floor level, such as below the level of concrete in which the pipe is encased. The tool includes a depth gauge drum and cutter head mounted on a shaft adapted to be driven by an electric hand drill. The cutter head or drum carries a bit which is urged into the work by springs and which includes a leading guide leg or finger for controlling the depth of the cut and a trailing cutting leg spaced from the guide leg to permit clearance of cuttings.

In the installation of toilet, shower and tub drains, it is commonpractice to locate PVC (polyvinylchloride) waste pipes, typically; of 2,3 or 4 inch diameter and with 1/4 inch wall thickness, in desiredpositions, with the pipes extending somewhat above the final .Iadd.floor.Iaddend.level, to then pour the concrete floor around the pipes, and,after the concrete has hardened, to cut off the waste pipes an inch ortwo below floor level.

While various internal pipe or tube cutters have been suggested, thesetend to be complex, of high cost, slow in operation, and have eitherbeen difficult to control or have required repeated, time consumingadjustment as the cut deepens. For example, U.S. Pat. No. 3,883,950 --Kurtz is directed to an internal cutter for cutting plastic pipe encasedin concrete, and U.S. Pat. No. 2,700,818 -- Fisher shows an internaltube cutting arrangement including a depth gauge. Other U.S. Patentsdeemed of less pertinence to the present invention include No. 61,499 --Wright; No. 1,320,521 -- Allison; No. 1,748,099 -- Arnold; No. 2,764,812-- Thornson; and No. 2,842,843 -- Willard.

An object of the invention is to provide a simple and inexpensive tool,which is simple to operate, requires minimal adjustment and whichquickly and accurately cuts off a PVC or the like pipe at the desireddepth within the pipe, to leave a cleanly finished end of the pipe fromwhich the extra length has been cut.

A further object is to provide a tool which will cut off the pipe in aplane normal to the pipe axis.

The novel features which are believed to be characteristic of thisinvention are set forth with particularity in the appended claims.

The invention itself, however, both as to its organization and method ofoperation, together with further objects and advantages thereof, maybest be understood by reference to th following description taken inconnection with the accompanying drawing, in which:

FIG. 1 is a side elevation of a tool in accord with the invention andwith the cutting bit fully extended;

FIG. 2 is an end view thereof taken along line 2--2 of FIG. 1, on anenlarged scale, showing the bit in fully retracted position;

FIG. 3 is a sectional view thereof taken along line 3--3 of FIG. 1 onthe scale of FIG. 2 and showing the bit in fully extended position;

FIG. 4 is a sectional view taken along line 4--4 of FIG. 3;

FIG. 5 is an exploded view partially in section of the cutter head, ordrum, assembly of the tool;

FIG. 6 is a detail sectional view taken along line 6--6 of FIG. 5;

FIG. 7 is a back elevational view of a portion of the cutter bit on afurther enlarged scale;

FIG. 8 is a front elevational view of such portion similar to FIG. 7;

FIGS. 9 and 10 are side elevational views of such portion taken,respectively, along lines 9--9 and 10--10 of FIG. 8;

FIG. 11 is an end view of the bit on the scale of FIGS. 7- 10;

FIG. 12 is a side elevational view, partially broken away and insection, on the scale of FIGS. 4- 6, showing the tool in operativerelation of a waste pipe and concrete floor and indicating, in brokenlines and exploded position, a finishing flange for the pipeinstallation;

FIG. 13 is a view similar to FIG. 12 showing the completed pipeinstallation with the finishing flange in final position.

Referring to FIG. 1, the tool comprises a metal shaft 1, which may be,typicaly, about one foot in length, having a threaded round end portion2, shown in broken lines, threaded into a solid metal drum or headmember 3, and an opposite end portion 4 adapted for chucking in a 1/2inch electric hand drill. Entrained on the shaft is a centering anddepth-determining drum 5 including a laterally extendingpipe-end-engaging flange 6 on its side away from the cutter drum or headassembly .[.2..]. .Iadd.12. .Iaddend.The drum is slideable along theshaft and is lockable in selected position along the shaft by a setscrew 7 threaded into collar 8 which is integral with the drum 5. Theshaft 1 may be round as shown, or it may be of hexagonal cross sectionto provide additional strength and a better seat for the set screw. Theshaft may further include depth scale markings therealong to aid inpositioning the drum 5 for desired depths.

The cutter drum or head member 3 carries a cutter bit 9 retained by aface plate 19 held to the member 3 by four screws 11.

As seen in more detail in FIGS. 2- 6, the cutter head assembly 12comprises the cylindrical drum member 3 having a rectangular groove orchannel 13 in which bit 9 fits with a sliding fit, a limit pin 14 fittedinto a bore 15 in the drum member and extending into a delimiting slot16 extending longitudinally of the bit, compression springs 17 retainedin an enlarged extension 18 of channel 13, a flat face plate, frontcover or retainer plate 19, and cover retaining machine screws or bolts11. The back of the drum is bored and screw threaded as seen at 20 tomount the drum on the shaft. The enlarged channel for housing thesprings may have a central partition 21 for separating and aligning thetwo springs, and a retaining lip 22 is preferably provided at theforward end of the spring channel 18 for convenience in assembly. Suchassembly is accomplished by seating the springs against the seat 23 atthe rear end of the spring housing channel and partially compressing thesprings until they are disposed in channel 18 and retained between theseat and lip, by inserting pin 14 in its bore, positioning bit 9 inchannel 13, and by then bolting the cover plate 19 to the drum. The bitor springs may be readily replaced by removal of the cover plate.

The bit is shown in FIGS. 3 and 4 in fully extended position with pin 14engaged against the inner end of slot 16. The bit may be manually pushedagainst the springs into the fully retracted position shown in FIG. 2,thereby compressing th springs by forcing the spring ends away from lip22. The channel 13 is proportioned to retain the bit in a close butfreely sliding fit, both along the sides of the bit and between thecover plate and the bottom of the channel 13.

The operative end of the bit includes a leading leg L and a cutter legC, the latter extending slightly further from the center of the drumthan the former. The cutter assembly as seen in FIGS. 2 and 3 would thusbe rotated counterclockwise during the cutting of the pipe.[.;.]..Iadd...Iaddend.

The cover plate 19 is provided with an opening 24 to pass chips cut fromthe pipe material by the cutting bit. The legs C and L of the bit 9 arepreferably beveled along their leading edges as shown at 25 and 26,respectively. The beveled portion 25 of leg C thus directs chips throughopening 24. The leading edge of leg L may trim off any unevenness alongthe sides of the cut, and the bevel 26 assists in clearing away suchchips, or any chips left in the groove cut by the cutter.

The bit is shown in greater detail in FIGS. 7- 11. Arrows 27 in FIGS. 7,8 and 11 indicate the direction in which the bit moves. It will be seenthat the cutting tip 28 of leg C extends outwardly beyond the end 29 ofleg L. Typically, with the tool in operative position in a pipe, beforecutting has commenced and with tip 28 engaged with the inner surface ofthe pipe, the end 29 of leg L will be approximately, 0.006 inches fromthe pipe surface. If, as so measured, the length of leg L is more than0.006 inches less than the length of leg C, taken to the cutting tip 28,chattering may be excessive. If leg L is only 0.002 inches shorter thanleg C, harder materials may be cut and chattering is minimized but thetime required to cut through the pipe wall will be increased. Withcertain pipe materials, with careful cutting speed adjustments, and withunworm bits carefully fitted in the drum recess, successful cuts may bemade with as much as 0.01 inches difference in length between legs L andC, and it will be apparent that a difference in such length of less than0.002 inches will provide an operative tool although the depth of cutper revolution would then be unnecessarily slow for PVC pipe or formaterials of comparable thickness and hardness.

The face 30 of the bit is disposed toward cover plate 19, and, as seenin FIGS. 9 and 10, the end surface 29 of leg L and the end surface 31 ofleg C are relieved or beveled away from face 30 at angles 32 and 33 ofabout 6° in each instance. The end surface 29 of leg L, as seen in FIGS.7 and 8, is, preferably, in the plane of the bit, arcuate onsubstantially the radius of the drum 3. The planar surface 31 of leg Cis relieved or beveled away from cutting tip 28 at an angle 34 of,typically, 18°, although this angle may be less for large diameter pipe,or for cutting harder and tougher materials than PVC, or if less strongmaterials are employed in the bit. A greater angle might be selected toslightly enhance the cutting speed or for small pipe, since, of course,the trailing end of the cutting leg face 31 should not touch the bottomof the groove being cut in the pipe.

It will be understood that the angles given for the ends of the bit legsare taken with respect to planes or lines normal to the longitudinalaxis of the bit. The angles 35 and 36 of the bevels 25 and 26 shown inFIG. 11 are typically each 12° with respect to a plane perpendicular tothe plane of the bit. The bit has, typically, a length equal toapproximately the radius of the cutting head drum, and a maximumextension of approximately 1/2 inch. It may be 1/8 inch thick and 1/2inch wide, and is formed of tool steel suitably tempered to hold a sharpcutting tip 28 and cutting edge though hundreds or thousands of cuts.

The cutting head .[.assemble.]. .Iadd.assembly .Iaddend.12 is shown inFIG. 12 in operative position in PVC pipe 37, with bit 9 cutting intothe pipe inner wall and producing chips 38 which fall freely throughopening 24 in cover plate 19. The flange 6 of depth gauge drum 5 isengaged against the exposed upper end 39 of the pipe. The bodies of thedrums 5 and 3 fit closely within the pipe whereby, even though edge 39of the pipe may be uneven and not in a plane normal to the pipe axis,cutting bit 9 cuts off the pipe in such a plane.

In a typical installation, the pipe 37 is encased in a concrete floor 40having a surface or level 41 below which the pipe is to be cut off. Aspace 42 surrounding the pipe and extending through and about one inchbelow surface 41 is provided to receive the tubular portion 43 of afinishing flange member 44.

FIG. 13 shows the pipe 37 as cut off to appropriate length and withflange member 44 in place with its tubular portion 43 glued or cementedby glue 45 to the pipe 37 to complete the installatin ready for thereception of toilet or drain fittings.

The drums and the cover plate 19 may be machined from aluminum alloy orother metal or may be more economically cast in substantially the finaldesired shape and then machine finished as is well known in the art.

While the drums may be completely solid as shown, it is, of course,possible to save weight and materials by forming the drums with hollowswhile leaving sufficient material by way of ribs or webs to provoideappropriate strength and rigidity, particularly if the drums are made bycasting.

It will be seen that, by providing a long shaft, the cutting head drummay be positioned to cut off the pipe as much as several feet from itsend. If a long shaft is so employed, it may be desirable to provide oneor more steadying collars, such as drums identical to drum 5 but withoutflange 6, along the shaft between the depth gauge and cutter head tominimize shaft whip.

While the invention has been described with respect to a certainspecific embodiment, it will be appreciated that many modifications andchanges may be made by those skilled in the art without departing fromthe spirit of the invention. It is intended, therefore, by the appendedclaims to cover all such modifications and changes as fall within thetrue spirit and scope of the invention.

What is claimed as new and what it is desired to secure by LettersPatent of the United States is:
 1. An inside cutter for cutting off at adesired level below the concrete surface, plastic pipe of predetermineddiameter encased in concrete, such pipe having an end exposed outwardlyof the concrete surface, comprising, a shaft having an end portionadapted for connection to shaft rotating means, a cutting head drum anda guide drum mounted on said shaft, first means for mounting said guidedrum on said shaft, second means for fixing said cutting head drum onsaid shaft for rotation therewith, one of said first and second meansbeing selectively releaseable to permit adjustment of the distancebetween said drums, said guide drum comprising a cylindrical portiondisposed toward said cutting head drum and an outwardly extending flangeportion disposed away from said cutting head drum and adapted to engagethe end surface of the exposed end of the pipe, said cutting head drumcomprising a cylindrical body portion and a cutting bit movablysupported thereon and projectable laterally thereof, said bit comprisinga leading leg and a trailing cutting leg terminating outwardly in anoutward cutting edge disposed outwardly a short distance beyond theouter end of said leading leg as measured radially from the axis of saidcutting head drum, said cylindrical portion of said cutting head drumbeing proportioned to fit closely within and to be freely rotatablewithin the pipe, and spring means engaged between said body portion andsaid cutting bit oriented to urge said bit laterally outwardly of saidcutting head drum operative to cause said cutting edge to cut to a epthdepth by engagement of said leading leg with the inner surface of suchpipe as said cutting head drum is rotated therein.
 2. An inside cutterfor plastic pipe of a predetermined internal diameter, comprising acutter head drum, means comprising a shaft for mounting and rotatingsaid drum, said drum being proportioned to fit closely and freelyrotatably within said pipe, said shaft and drum being coaxial, a cuttingbit, said drum having guide means extending perpendicularly radially ofsaid axis of said shaft and drum, said bit being carried in said guidemeans, spring means between said drum and bit urging said bit outwardlyalong said guide means, the bit having a bifurcated outer end portionincluding a cutting leg and a leading depth-control leg lying in thesame plane perpendicular to said axis, the cutting leg terminatingoutwardly in a cutting edge disposed at the edge of the cutting legoriented toward the depth control leg and the depth control legterminating outwardly at a distance from said axis of between about0.002 and 0.010 inches less than the distance of said cutting edge fromsaid axis.
 3. The combination according to claim 2 wherein a depth gaugedrum, having a body portion proportioned to fit closely within said pipeand a flange portion of greater diameter than said body portion andgreater than said internal diameter of said pipe, is disposed on saidshaft spacedly from said cutting head drum, and wherein selectivelyoperative locking means is provided on one of said drums for lockingsaid one drum along said shaft at an adjustable distance from the othersaid drum.
 4. The combination accoding to claim 2 wherein said cuttingbit has opposite faces and said cutting edge is beveled from one to theother of said faces.
 5. The combination according to claim 4 wherein theend of said leading leg is beveled in the same direction and at the sameangle as said cutting edge.
 6. The combination according to claim 2wherein said drum includes a cover plate detachably secured thereto,said cover plate forming a portion of said guide means and, uponremoval, exposing said cutting bit for removal and replacement.
 7. In aninside the tube cutter comprising a body member adapted to be disposedand rotated on a predetermined axis in a predetermined direction insidea tube, a bifurcated cutting bit comprising a cutting leg and a leadingcutting depth control leg, means slideably mounting said bit on saidbody member for sliding inwardly and outwardly thereof and with saidlegs extending outwardly of said member and lying in a plane normal tosaid rotational axis and with said leading leg disposed in saidpredetermined direction from said cutting leg, said cutting legterminating outwardly in a cutting edge disposed outwardly a shortdistance beyond the outer end of said leading leg as measured radiallyfrom said axis, and spring means between said body .Iadd.member.Iaddend.and bit urging said bit outwardly from said body member.
 8. Thecombination according to claim 7 wherein said mounting means mounts saidbit for sliding radially with respect to said axis.
 9. The combinationaccording to claim 7 wherein said cutting leg extends outwardly betweenabout 0.010 and 0.002 inches further than said cutting depth control legas measured radially from said axis.
 10. The combination according toclaim 8 wherein said cutting leg extends outwardly between about 0.010and 0.002 inches further than said cutting depth control leg as measuredradially from said axis. .Iadd.
 11. In an inside tube cutter comprisinga body member adapted to be disposed and rotated on a predetermined axisin a predetermined direction inside a tube, a bifurcated cutting bitcomprising a cutting leg and leading cutting depth control leg, andmeans slideably mounting said bit on said body member for slidinginwardly and outwardly thereof and with said legs extending outwardly ofsaid member and lying in a plane normal to said rotational axis and withsaid leading leg disposed in said predetermined direction from saidcutting leg, said cutting leg terminating outwardly in a cutting edgedisposed outwardly a short distance beyond the outer end of said leadingleg as measured radially from said axis..Iaddend..Iadd.
 12. Thecombination according to claim 11 wherein said mounting means mountssaid bit for sliding radially with respect to said axis. .Iaddend..Iadd.13. The combination according to claim 11 wherein said cutting legextends outwardly between about 0.010 and 0.002 inches further than saidcutting depth control leg as measured radially from said axis..Iaddend..Iadd.
 14. The combination according to claim 12 wherein saidcutting leg extends ouwardly between about 0.010 and 0.002 inchesfurther than said cutting depth control leg as measured radially fromsaid axis. .Iaddend..Iadd.
 15. The combination according to claim 11including means in contact with said bit for urging said bit radiallyoutwardly with respect to said rotational axis..Iaddend.